gerously close to Southern California. There are uncon- 

 firmed reports of zero temperatures in the eastern and far 

 southern portions of this district. Weather Bureau temper- 

 atures 10 degrees below freezing- were registered at 5 A. M. 

 of the 7th at San Luis Obispo, on the coast, just south of Point 

 Conception. 



The Heavy Rain in February. 



The causes which led up to the heavy rain in Los An- 

 geles on February 24, 25 and 26 were both general and spe- 

 cific. By general, is meant the geographical distribution of 

 atmospheric pressure on the Pacific Coast and the region west 

 of the JViississippi River, and specifically, local as affecting tne 

 San Gabriel valley. 



The records of Southern California stations show that 

 during dry seasons, i. e., seasons with abnormally deficient 

 precipitation, downpours in Tanuarv, February or March are 

 comparatively common, with their relative frequency like 

 this : 



January, I, 



Februarv, 3, 



March, 2. 



The reason is this: The difference between a season of 

 deficient rainfall and excessive or normal rainfall is whether 

 or not the areas of low pressure (which normallv move in and 

 strike the Coast about the latitude of the Columbia River) 

 take a course a little south of east and move slowly on their 

 path to the Great Lakes, or whether these barometric deores- 

 sions are blocked bv great areas of high pressure that drift 

 down from the British Provinces and envelop the western 

 states. The general blocking of the normal movement gives 

 long periods of dry, cool and clear weather to California, and 

 especially to Southern California. 



During seasons of deficient precipitation the high areas 

 prevent the general movement of the regular northern storms. 

 Owing to the crests of these high areas being north of this 

 district, most frequently over Nevada and Utah, a solid front 

 is presented to the west but is weakest towards the south. To 

 this spot a small, but frequently well-defined, low area breaks 

 in and enters the southern coast. 



Such a depression was first observed over Southern Ari- 

 zona on the 19th, it having probably entered the Sonora re- 

 gion on the 18th. This storm moved rapidly up the valley on 

 the 20th and on the 21st rain began to fall in Los Angeles, 

 accompanied by a northerly wind, thus indicating the south- 

 ern and consequently abnormal origin of the storm. The 

 storm continued its northerly course, but dipped southerlv 

 on the 22d, which day was clear and bright all day, but with 



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